How to invoke a script when closing any file with a given extension

Question

Is it possible to automatically invoke a given applescript when closing -any- file with a given extension in a specified folder (and subfolders)?

If not in AS, is this possible in bash? (The AS I am considering simply calls a bash script.)

Answer 1

If the script could also be run when you open a file (or in other cases), you could use opensnoop.

~/test:

#!/bin/bash

while :; do
    opensnoop | grep -Ev ' (mdworker|mds|filecoordinatio|revisiond|Finder|Alfred) ' | grep -m1 '/Users/username/Folder/.*\.txt'
    say a
    sleep 1
done

/Library/LaunchAgents/test.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC -//Apple Computer//DTD PLIST 1.0//EN http://www.apple.com/DTDs/PropertyList-1.0.dtd>
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>test</string>
    <key>Program</key>
    <string>/Users/username/test</string>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>

chmod +x ~/test, sudo chown root /Library/LaunchAgents/test.plist, and launchctl load /Library/LaunchAgents/test.plist.